The present disclosure relates to mirrors and, more particularly, to a convex mirror having multiple reflecting surfaces, each having a respective curvature.
To enhance safety during operation thereof, many vehicles, for example trucks, buses and automobiles, employ mirror systems that enable the drivers of the vehicles to see behind and/or to the side of the vehicle without turning their head in that direction. Such mirror systems typically include an interiorly-located mirror, commonly known as a “rear view” mirror, mounted in proximity to the upper interior side surface of the windshield, and a pair of exteriorly-located mirrors, commonly known as “side view” mirrors, respectively mounted on a forward portion of the door assemblies for the driver and front seat passenger.
Most mirrors used to enable a driver to look behind or to one side of a vehicle may be classified as flat, convex or aspherical mirrors. A flat mirror has a generally planar surface that tends to produce true and undistorted reflections of objects. However, because the field of vision produced by the planar reflective surface is relatively narrow, e.g. is typically bounded by planes generally orthogonal to the edges of the reflective surface, flat mirrors are characterized by a relatively large blind spot. In contrast, a convex mirror has a curved reflective surface and, when compared to a flat mirror, is generally characterized by a greater field of vision and a smaller blind spot. Indeed, as the curvature of the reflective surface is increased, the field of vision for the convex mirror increases while the size of the blind spot decreases. Thus, a mirror having a convexly curved reflecting surface will rectify many of the shortcomings of a mirror having a generally flat reflective surface. Unfortunately, convex mirrors are not without their own shortcomings, most notably, distortions in the images of objects reflected thereby and difficulties when attempting to accurately judge the distance separating the mirror from the reflected objects. Furthermore, the severity of these shortcomings tends to worsen as the curvature of the reflective surface increases.
An aspherical mirror typically includes two or more convexly curved mirror surfaces, each of which is curved to a different extent. For example, one aspherical mirror known in the art includes primary and secondary mirror surfaces. The primary mirror surface encompasses approximately two-thirds of the aspherical mirror and is a convex mirror having a relatively small curvature of the reflective surface which causes the primary reflective surface to approximate that of a flat mirror. Accordingly, reflections appearing in the primary reflective surface are true and undistorted. The secondary mirror surface, on the other hand, covers approximately one-third of the aspherical mirror and is a convex mirror having a larger curvature of the reflective surface relative to the curvature of the primary reflective surface. Accordingly, the secondary mirror compensates for a portion of the relatively narrow field of view and the blind spot characterizing flat mirrors such as the primary reflective surface. The transition from the primary reflective surface to the secondary reflective surface is smooth, thereby minimizing any problems resulting from the difference between the undistorted image/smaller field of vision of the primary reflective surface and the relatively more distorted/greater field of vision of the secondary reflective surface. However, as most aspherical mirrors require a relatively large difference in the degree to which the secondary reflective surface is curved in order to remove any blind spots caused by the primary reflective surface, the transition between the primary and secondary reflective surface remains relatively sharp, and, as a result, continues to affect proper judgment of the distance separating the mirror and an object reflected thereby.
It should be readily appreciated that a multi-curvature convex mirror which combines the advantages of a larger field of view and a reduced or eliminated blind spot when compared to a flat mirror while simultaneously reducing the distortion and difficulty in estimating separation distances normally associated with convex mirror would enjoy many advantages over both flat and convex mirror currently in use. Such a multi-curvature mirror is described hereinbelow.